Synchronous Generator Sub-Transient Reactance Estimation Through Harmonic Measurements

In this paper, an alternative testing method is proposed for the estimation of the subtransient reactances of a synchronous generator. The method is based on the frequency conversion model, which describes the harmonic behaviour of synchronous machines. By injecting harmonic currents into the synchronous generator and evaluating the resulting electromotive force components, the subtransient reactances are estimated. It is shown that for an ideal machine in simulation, this method results in an exact prediction. Finally, a practical test setup has been built in order to validate the method. The reactance estimation is found to be accurate as compared to negative sequence test results.